Most modern automotive fuel systems utilize fuel injectors to provide precise metering of fuel for introduction into each combustion chamber. Additionally, the fuel injector atomizes the fuel during injection, breaking the fuel into a large number of very small particles, increasing the surface area of the fuel being injected, and allowing the oxidizer, typically ambient air, to more thoroughly mix with the fuel prior to combustion. The metering and atomization of the fuel reduces combustion emissions and increases the fuel efficiency of the engine. Thus, as a general rule, the greater the precision in metering and targeting of the fuel and the greater the atomization of the fuel, the lower the emissions with greater fuel efficiency.
An electromagnetic fuel injector typically utilizes a solenoid assembly to supply an actuating force to a fuel metering assembly. Typically, the fuel metering assembly includes a seat and closure member, which reciprocates between a closed position, where the closure member is seated in a seat to prevent fuel from escaping through a metering orifice into the combustion chamber, and an open position, where the closure member is lifted from the seat, allowing fuel to discharge through the metering orifice for introduction into the combustion chamber.
The fuel injector is typically mounted upstream of the intake valve in the intake manifold or proximate a cylinder head. As the intake valve opens on an intake port of the cylinder, fuel is sprayed towards the intake port. In one situation, it may be desirable to target the fuel spray at the intake valve head or stem while in another situation, it may be desirable to target the fuel spray at the intake port instead of at the intake valve. In both situations, the targeting of the fuel spray can be affected by the spray or cone pattern. Where the cone pattern has a large divergent cone shape, the fuel sprayed may impact on a surface of the intake port rather than towards its intended target. Conversely, where the cone pattern has a narrow divergence, the fuel may not atomize and may even recombine into a liquid stream. In either case, incomplete combustion may result, leading to an increase in undesirable exhaust emissions.
Complicating the requirements for targeting and spray pattern is cylinder head configuration, intake geometry and intake port specific to each engine's design. As a result, a fuel injector designed for a specified cone pattern and targeting of the fuel spray may work extremely well in one type of engine configuration but may present emissions and driveability issues upon installation in a different type of engine configuration. Additionally, as more and more vehicles are produced using various configurations of engines (for example: inline-4, inline-6, V-6, V-8, V-12, W-8 etc.,), emission standards have become stricter, leading to tighter metering, spray targeting and spray or cone pattern requirements of the fuel injector for each engine configuration.
It is believed that one approach to meeting emission standards in a fuel injector is to minimize the so-called “sac volume.” As it is used in this disclosure, sac volume is defined as a volume downstream of a closure member/seat sealing perimeter and upstream of the orifice hole(s), which can be also viewed as the volume of fuel remaining in the interior of the tip of the injector. This volume of fuel is believed to affect combustion and unwanted emission at the end of a fuel injection cycle, and therefore, it is believed that such sac volume should be minimized.
It is also believed that a metering disc can be deformed to provide a dimpled surface. Such dimpled surface is believed to allow a metering orifice to be oriented relative to a referential datum by a single included angle. However, by orientating the metering orifice with a single included angle, such metering disc apparently fails to permit targeting of the fuel spray consonant with the metering, spray targeting and spray or cone pattern requirements particular to each type of engines. Moreover, such metering disc, when used in a fuel injector, may cause the fuel injector to have a large sac volume that could affect combustion and unwanted emission in the engine in which such injector is utilized therein.